Most of Turning Tides lands in December, with a few features saved for January. I'm not sure why this is the case, however two new maps in Cape Helles and Achi Baba will land this side of Christmas. A new operation, Gallipoli—"take part in the British amphibious assault on the Gallipoli peninsula in 1915"—will arrive then too; as will the L-Class Destroyer and C-Class Airship, and a new elite class The Infiltrator.

Post-new year, Turning Tides brings with it the British Empire's Royal Marines as a new faction, and Heligoland Bight and Zeebrugge as new maps. The incoming expansion also adds a number of mini-challenges, service assignments, specialisations, unlocks, and a new 'Conquest Assault' game mode—the latter of which is described thusly:

Relentlessly press the offensive—or hold your ground. In a twist on the signature Conquest mode, Conquest Assault sees attackers and defenders fight over key areas, exclusively controlled by the defending team as the match starts.

Again, Battlefield 1's Turning Tides DLC is split between December and January. More information can be found this-a-way, while Phil's thoughts on the base game can be found over here.